State Highway 73 (SH 73) is a major east-west South Island state highway in New Zealand connecting Christchurch on the east coast with Cass/Hokitika via the Southern Alps. It is mostly two lane, with some single-lane bridges north of Springfield but is mostly dual carriageway in Christchurch. The fourth and fifth-highest points of New Zealand's state highway network are on this road at Porters Pass and Arthur's Pass respectively. History The route connecting the West and East coasts of the South Island via the Southern Alps were known for hundreds of years by the Māori people, due to a flourishing pounamu trade. The Europeans were informed of the route by a local chief in the mid-19th century but was not used during his lifetime. In 1864, Arthur Dudley Dobson traversed from the east to the west coast from the Waimakariri River, thereby discovering Arthur's Pass. A route connecting Christchurch to Hokitika was fully completed in 1866, with the first Cobb & Co coach began operating that same year for the burgeoning gold rush. Construction of a rail link had started in 1890, and the Midland Line between Canterbury and the West Coast was finally completed on 4 August 1923, with the opening of the Otira Tunnel. This signalled the end of the Cobb & Co coach in New Zealand. When the section of the line from Springfield to Broken River in Canterbury was opened in 1906, it was then possible to travel from Canterbury to the West Coast in a single day with a 40-mile (64 km) coach journey between the railheads at Broken River and Otira. Due to the geography and topography between Springfield and Kumara, the road has been subjected to several closures and road realignments, with both Porters and Arthur's Pass subjected to frequent closures during the winter months. The road between Arthur's Pass and Otira in particular was amongst the most dangerous in the country, due to the road located on scree slopes which frequently gave way. As a result, numerous studies were conducted into alternative options for fixing the road around Candy's Bend, Starvation Point and the Zig Zag. Construction of the Otira Viaduct and the protective roofs from slips began in 1997 and opened in 1999. Route Kumara Junction to Christchurch State Highway 73 begins 11 km south of Greymouth at Kumara Junction. The highway passes through undulating farmland, scrubland and forest as it